<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    * {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
    }

    .wrap {
        width: 1100px;
        height: 800px;
        margin: 0 auto;
        padding: 0;
        background-color: orange;
    }

    /* 辅助盒子，解决浮动换行问题：原理 width = mr+ml+width1
                                  1190 = -5+-5+1200  
因此扩展了子盒子box的宽度
*/
    .box {
        margin: 0 -2.5px;
    }

    li.item {
        float: left;
        list-style: none;
        margin: 0;
        width: 221px;
        height: 168px;
        border: 1px solid rebeccapurple;
        border-right: 0;
        margin-right: -1px;
        background-color: black;
        color: #fff;
    }
</style>

<body>
    <div class="wrap">
        <div class="box">
            <ul>
                <li class="item">1</li>
                <li class="item">2</li>
                <li class="item ">3</li>
                <li class="item ">4</li>
                <li class="item ">5</li>

            </ul>
        </div>
    </div>
</body>
<script></script>

</html>